"I reckon that the most useful network-debugging tool available
is Ethereal, but then I am biased as a part of the Ethereal team.
Ethereal is a packet capture and analysis tool that can display the
smallest detail of a large and ever increasing number protocols.
The current version of Ethereal is 0.8.15. Figure 2 shows Ethereal
displaying Label Distribution Protocol packets."
"Due to the efforts of various teams around the world that have
ported GTK+ and libpcap to Windows, you can now run Ethereal under
Windows as well. SMB, the protocol underlying Microsoft Windows
Networking, is now among the growing number of protocols that
Ethereal understands. So it is even possible to diagnose many
Windows Networking problems with Ethereal."
"Watch out though! Just recently the Ethereal team discovered a
problem (caused by a chain of problems) with the SMB decode for the
Windows version of Ethereal. Windows NT does not return the correct
date information when responding to a Get File Attributes SMB
command. That causes the Windows gmtime routine to return NULL
rather than a pointer to a string. Ethereal would blindly index
into the string and crash. Under Unix Ethereal happily reported
file times well before 1970! Oh well, the bug is fixed now, or it
will be when the next version of Ethereal is released. That is yet
another demonstration of the power of open source software. Because
the source is available, anyone can fix the problems."